Binding referendum requires a legal implementation as a part of
the ratification-process. Consultative referendum can anyhow be
held if ordered by ad-hoc-law (UK has no written constitution).

PROCEDURE

The
government introduced on 30 October 1997 a bill into Parliament
“to make provision consequential on the Treaty signed at Amsterdam”
(European Communities (Amendment) Act 1998, Acts 1998 Chapter 21,
11 June 1998). The House of Commons (lower house) approved on 19
January 1998 (370 in favor, 145 opposing). The House of Lords (upper
house) approved the ratification bill on 11 June.